Arcto-Tertiary Geoflora
The Arcto-Tertiary Geoflora[a] is a hypothesized floral assemblage that once covered the Northern Hemisphere, from roughly the late Mesozoic to mid Cenozoic Eras.
Origins
[edit]First proposed by the paleobotanists J.S. Gardner and C. Ettinghausen in 1879, the concept was intended to answer questions about the disjunct distribution of identical or closely related plant species: for instance, magnolia and tulip trees are native to both the Southeast United States and southern China and Indochina.[2][3]
As envisioned, the ATG had a wide distribution when the global climate was much warmer than it is currently, a situation strengthened by the closer position of some of the continents in late Mesozoic to early Cenozoic times.[4][5] With the onset of global cooling and the Ice Ages, the ranges of these tropical to subtropical species were left in isolated pockets of warmer climates.[6]
The southern, more tropical equivalent of the ATG was the Neotropical Tertiary Geoflora.[a][6]
Footnotes
[edit]- ^ a b This designation has as a part of it a term, 'Tertiary', that is now discouraged as a formal geochronological unit by the International Commission on Stratigraphy.[1]
- ^ Ogg, James G.; Gradstein, F. M.; Gradstein, Felix M. (2004). A geologic time scale 2004. Cambridge, UK: Cambridge University Press. ISBN 0-521-78142-6.
- ^ Delcourt, Hazel, Forests in Peril (Blacksburg: The McDonald and Woodward Publishing Company, 2002), 31-2.
- ^ Dougal Dixon et al., The Atlas of Life on Earth (New York: Barnes & Noble Books, 2001), 334-5.
- ^ Delcourt, 31.
- ^ Dixon et al., 334.
- ^ a b Delcourt, 32.